1. Field of Use
This invention relates to computer systems and, more particularly, to methods of decreasing the size of swap space on UNIX type operating system based computer systems.
2. Description of the Related Art
Computer systems are information handling systems which can be designed to give independent computing power to one user or a plurality of users. Computer systems have attained widespread use in providing computer power to many businesses and institutions. Some important applications in which computer systems have become common include manufacturing monitoring and control; electrical, mechanical, and chemical system design and simulation; and network management and service. Productive processing time is of great importance to the users of these computer applications because system down time can result in significant costs.
Computer systems are designed to provide a degree of system availability that is necessitated by the applications for which the computer system is intended. System availability ranges from the ability of a system to remain functional in spite of failures in a portion thereof, to the minimization of a system's down-time in the event of a failure or necessary upgrade. High availability (HA) computer systems, as their name implies, are required to be available, or "on," virtually all of the time. For example, because many computer applications involve the use of network servers to provide processing power to multiple users, it is important that the network server be available as much as possible. Such computer systems (or networks of such computer systems) should be capable of being upgraded with minimal system down time.
High availability computer systems must be able to restart as soon as possible after a system upgrade. System upgrades or patches are often necessitated by the establishment of new system requirements. Unfortunately, performing a system upgrade such as resizing the swap space on a UNIX based computer system typically requires that the computer system be powered down or turned off, and that the operating system be reinstalled with the required changes.
Commonly, when a computer system requires an upgrade, patches are made to the operating system of the computer system. Often, new patches are added to the patches from a previous system upgrade resulting in a large number of patches for each successive upgrade. The successful patches are then updated to other computer systems by replacing the present operating system of those computer systems with the new operating system including the successful patches. The new operating system is often installed from a storage device such as a tape drive to directly replace the present operating system needing the upgrade. Alternatively, the new operating system can be downloaded over a network.
Use of the method set forth above has certain consequences. Notably, using this method usually requires that the computer system be shut down. A backup of the present operating system usually must be made, and the upgrades or patches must be loaded while the computer system is down. Additionally, upgrades must often be made for multiple computer systems, causing down-time for all the systems involved. For example, in a network of servers, each server must be upgraded individually. That is, the system manager must power down a server, thereby limiting server availability by preventing user access, make a backup of the present operating system, load the new operating system, and test the new operating system. The system manager then repeats these actions for each of the other servers. The computer system being upgraded is usually down throughout the procedure, possibly for a period of hours. The cost for system downtime during these upgrades can be significant. Also, the chances for error or failure can be significant with this practice.
An alternative method allows upgrading a computer system while the computer system is operating. An operating system may be upgraded by selecting and preparing a new boot device while the computer system is functioning, loading the new operating system onto the new boot device while the computer system is functioning, and rebooting the computer system using the new boot device. Such a method of upgrading computer systems is disclosed in U.S. patent application Ser. No. 08785,491, attorney docket No. M-4525 US, filed on Jan. 17, 1997, entitled "Installing Operating Systems Changes on a Computer System," naming Danny B. Gross, Michael D. O'Donnell and Gene R. Toomey as inventors.